Crystal structures of two tropinone reductases: Different reaction stereospecificities in the same protein fold

Keiji Nakajima, Atsuko Yamashita, Hiroyuki Akama, Toru Nakatsu, Hiroaki Kato, Takashi Hashimoto, Jun'ichi Oda, Yasuyuki Yamada

Research output: Contribution to journalArticlepeer-review

111 Citations (Scopus)

Abstract

A pair of tropinone reductases (TRs) share 64% of the same amino acid residues and belong to the short-chain dehydrogenase/reductase family. In the synthesis of tropane alkaloids in several medicinal plants, the TRs reduce a carbonyl group of an alkaloid intermediate, tropinone, to hydroxy groups with different diastereomeric configurations. To clarify the structural basis for their different reaction stereospecificities, we determined the crystal structures of the two enzymes at 2.4- and 2.3-Å resolutions. The overall folding of the two enzymes was almost identical. The conservation was not confined within the core domains that are conserved within the protein family but extended outside the core domain where each family member has its characteristic structure. The binding sites for the cofactor and the positions of the active site residues were well conserved between the two TRs. The substrate binding site was composed mostly of hydrophobic amino acids in both TRs, but the presence of different charged residues conferred different electrostatic environments on the two enzymes. A modeling study indicated that these charged residues play a major role in controlling the binding orientation of tropinone within the substrate binding site, thereby determining the stereospecificity of the reaction product. The results obtained herein raise the possibility that in certain cases different stereospecificities can be acquired in enzymes by changing a few amino acid residues within substrate binding sites.

Original languageEnglish
Pages (from-to)4876-4881
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume95
Issue number9
DOIs
Publication statusPublished - Apr 28 1998
Externally publishedYes

ASJC Scopus subject areas

  • General

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